Organic light-emitting devices are a type of light-emitting device that includes a thin film containing a fluorescent organic compound interposed between an anode and a cathode. When electrons and holes are injected from the respective electrodes, excitons of the fluorescent compound are generated and the organic light-emitting device emits light as the excitons return to their ground state.
The recent advancement of organic light-emitting devices has been remarkable. Organic light-emitting devices make it possible to produce thin and light-weight light-emitting devices that have high luminance at a low application voltage and a wide variety of emission wavelengths and display rapid response. This suggests that the organic light-emitting devices can be used in a wide variety of usages.
However, presently, there remains room for improvements. To be more specific, emitted light needs to have a higher luminance and the optical conversion efficiency needs to be increased for practical applications. Moreover, improvements are needed in terms of durability, such as changes with time caused by long use and deterioration caused by oxygen-containing atmospheric gas and humidity. In order for the devices to be applicable to displays of portable appliances, the power consumption of the devices needs to be low. In particular, electron injection/transport materials which are constituent materials of electron injection layers and electron transport layers affect the driving voltage, the emission efficiency, and the lifetime of organic light-emitting devices. Thus, research and development on the electron injection/transport materials have been actively pursued. However, the current situation does not sufficiently address the aforementioned challenges. When devices are used as constituent parts of full color displays, deterioration of blue pixels proceeds fastest. Thus, materials that increase the efficiency and extend the lifetimes of blue light-emitting devices are desired.
One of the approaches to address these challenges is the proposal of organic compounds having phenanthroline and anthracene backbones. Attempts have been made to use such organic compounds as the constituent materials of the electron injection layer and the electron transport layer of an organic light-emitting device (refer to PTL 1 to PTL 4). However, their emission hue, emission efficiency, luminance, and durability need to be improved further.
NPL 1 proposes an organic compound having a 4,10-diazachrysene backbone and a synthetic method therefor.